Method of washing gravel



m 26, 1929. F R, BRAVO 1,737,004

' METHOD OF" WASHING GRAVEL Qriginal Filed March 20. 1928 3 Sheets-Sheet l Nov. 26, 1929. I F. R. DRAVO 1,737,004

METHOD OF WASHING GRAVEL ori inal Filed March 20. 1928 3 Sheets-Sheet 2 INVENTOR Nov. 26, 192 F. RDRAvo' 1,731,004

METHOD 01 WASHING GRAVEL Original Filed March 20. 1928 3 sheets-sheet s INVENTOR N z. *prd I Patented Nov. 26, 1929 UNETE STATES FRANCIS R. BRAVO, OF EDGEWORTH, PENNSYLVANIA, ASSIGNOR TO THE DRAVO CON- TRACTING COMPANY, OF CI-IARLEROI, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA METHOD OF WASHING GRAVEL Original application filed March 20, 1928, Serial No. 263,058.

Divided and this application filed August 8,

1929. Serial No. 384,262.

My invention relates to improvements in the washing of gravel and other small masses to separate it from material of different size with which it may be associated. The primary object of the invention is expeditiously to separate and cleanse sand and gravel taken from river beds and other places of deposit, removing from it associated material and leaving it suitable for use for building pur- 19 poses. This application is a division from an application for United States Letters Patent, filed by me March 20, 1928, Serial Number 263,058.

A gravel washer or scrubber, in the operation of which the method of my invention may be performed, is illustrated in the accompanying drawings. Fig. I is a diagrammatlc view in elevation of a sand and gravel plant in which is included the washer or scrubber of my invention. Fig. 11 is a View in section, on the plane indicated at II1I, Fig. I. Fig. T11 is a view to larger scale, showing partly in elevation and partly in axial section, the wash er in which the invention centers. Figs. TV and V are views in transverse section, on the planes indicated at IV-IV and V-V,

III.

The various pieces of apparatus which make up a sand and gravel plant are suitably 3 placed and supported, with reference to the deposit to be worked. By way of example I of the inner shell are larger than the perforashow an arrangement suitable for work upon a deposit which constitutes a river bed, and accordingly the plant includes a barge, upon which the washer may be understood to be supported. Otner pieces of apparatus may be understood to be supported on this or on adjacent boats, or elsewhere, as may be convenient. The washer or scrubber is indicated at 1 and the barge which carries it, at 2.

The washer or scrubber is essentially an elongate structure here shown to be cylindrical and supported for rotation, with its axis at an angle to the horizontal. Its walls are perforate in part, and it is designed to re-' ceive through its higher'end the material to be washed and to discharge at its lower end so much of the material as has not in the scrubbing operation passed ti "or 93h the per rate were. It/i,. ;s are for caus long and}? feet in ing washing streams of water to penetrate the mass of material within the cylinder. The washer or scrubber 1 is in the drawings shown to be mounted for rotation, by resting upon spools 3, some or all of which may be understood to be power-driven. The water for washing the material enters the cylinder chamber through a pipe 4. Material is supplied to the cylinder by an elevator 5 equipped with buckets. The elevator scoops material from the river bed and delivers it by a suitable chute 6 through the upper head of the cylindrical washer 1. The cylinder is a compound one and includes an inner cylindrical shell, to which the numeral 1 is immediately applied, and an outer cylindrical shell 7. The outer shell is greater in diameter and less in length than the inner; the two cylindrical shells are coaxially arranged, the outer is conveniently borne by the inner, as upon the posts 8 and, at the upper end, upon an annular diaphragm 81. The inner shell is throughout the two end regions 11 and 13 perforate, and throughout an intermediate portion 12 imperforate. The outer shell is in its higher portion 71 perforate and in its lower portion 72 imperforate; and the imperforate portions 12 and 72 of the two shells are preferably arranged,

portion 72- surrounding portion 12.

The perforations in the higher portion 11 tions in the higher portion 71 of the outer shell, and ordinarily the perforations in portion 11 will be smaller than those in the lower portion 13 of the inner shell. Specifically, the perforations in portion 11 may be of the order of 1 inches across; those in portion 71, of the order of of an inch (this portion will advantageously be formed as shown, of netting) those of portion 13 may be of the order of3inches across. It will be understood that the particular dimensions may vary, to meet particular conditions, and to afford a product of desired range in grade. The inner shell may be 24 feet long and 6 feet in diameter, the outer may be 13 feet diameter. The portions 11 and, i. a he two shells may extenclfrom the in.

longitudinally far '5 feet; and

the portions 12 and 72, for 6 feet. The lower ends of both shells are open for the discharge of material.

The imperforate portions 12 and 72 of the two shells are equipped internally with inwardly extending blades or heaters 14 and is. conveniently arranged in staggered rows, and extending obiiquely upon the shell walls.

The water pipe 4 is continued in branches ll and 12 which extend longitudinally within the inner cylindrical space and within so much at least of the space between the two shells as is defined by the shell portions 12 and 7 2, and these pipes are provided withnozzles adapted to direct jets of water upon material resting upon the rising wallsof the turning shells, as best indicated in Fig. IV.

iilateri'al dredged from the river bed is, in the practice of the method of my invention, fed through chute 6 primarily tothe inner shell a't its upper end. The material may be understood to include, mixed with the desired sand and gravel, cobbles of larger size, which are not desired, or whi'ch't'o the advantage of further separating operations may be initially separated, and sticky clay and silt which are not desired. Clay particularly when present exists in coherent masses, and these masses in the separating apparatus tend to form balls gathering up and entrapping in their mass, sand and smaller pebbles; and it is particularly a difficult problem to dissipate and wash out these masses of clay, recovering the desired materials entrapped in them.

The material in its native state entering the portion 11 of the inner cylindrical shell assumes as the washer rotates (counter-clockwise, as seen in IV) the position indicated at A in Fig. IV. So spread upon the wall of shell portion 11 it is'sub 'ected to streams of water projected 'from nozzlesu'n pipe section 41. The water may be supplied under a pressure of say, pounds to the square inch. The material so beat upon by water and tumbled by the rotating cylinder is broken up, and particles less in diameter 'tliai'i 1 inches escape through theperfoi'atime into the portion 71 of the outer shell. The material'which soesca pes is muddy water (sonic of the clay and substantially all of the silt beii'ig already in suspension) separated sand and pebbles, and the sm'allpr nodules and balls of clay. So much otthematerial under treatment asdoes not 'so escape through the perforations in shell portion 11, advances as the washer rotates, to the shell portion 12.

Of the material which falls through the p f tor'ations otshell section '11 to the outer shell, the finer particles escape through the j/ -inch meshes. The particles so escaping are sand, small'pebbleS, and bits of clay of such small size that they are substantially dissipated intheir ntirety in the further treatment. The material so escaping is caught below in a hopper 9 and directed into a tank "dri'ca l sieve 10. So much of the material passing to the outer cylinder as fails to escape through the perforate shell portion 71, advances as the washer rotates, to the shell portion 72.

, The shell portions 12 and 72 are imperforate,"and as the washer rotates the blades with which they are interiorly equipped raise and tumble the material, and as the material is by such means raised and tumbled, it continues to be subject to the washing action of the jets of water, and here the jets from pipes l2 act on the material within the outer shell, while the et-s from pipe 11 continue to act on the material within the inner shell. The ellect of tumbling and washing in this blind that is to say, impertorate) portion of the washer isto'complete the dissipation of masses of clay.

From the open lower end of the outer cylinder, sand and pebbles liberated from the agglomeration with clay pass to the hopper 9 and thence to tank 10, and the clay also passes to the tank, but in proper condition for separation. The masses are broken up and the finely divided clay continues in suspension in the body of water. That is to say the water is muddy. This muddy water is discharged from the tank through an overflow. Similarly in shell portion 12 the bodies of clay are broken up and the clay goes into suspension in the wash water. Thematerial in the inner shell, however, carries larger pebbles and cobbles which have still to be separated. Accordingly the inner shell is prolonged in the portion 13, and the material washed in section 12 advances as the washer continues to rotate, into section 13. The walls 'ofsection 13 are perforated with large perterations (in this instance, of the order of 3 inches) and the material continues to be subject to the streams of wash water projected from the nozzles of pipe 41. The-consequence and efiect is that the fines,- the muddy water, the sand, and the 'gravel' all escape to hopper 9 and thence to tank 10, while nothing remains to escape from the open end of the inner shell but the larger cobbles of about 3 inches in diameter and upwards. These large cobbles so escaping may be returned to the river bed, or they may be accumulated in a suitable receptacle 20.

A bucket elevator 21 is arranged to elevate fromtanl'r 10 and -to discharge into other suitable separating apparatus the sand and smaller pebbles, while the muddy water falls away. The further separating apparatus may include, for example, a revolving cylin- 22 of familiar construction adapted to eflect separation of the larger pebbles, ranging in size from, say, 1 inches ii diameterto 3 inches, andthe medium-sized pebbles, ranging in size from 4' of an inch 'to i'i'iches, 1fro'in the fines. The larger pebbles are delivered from the open lower end 23 of sieve 22, the medium-sized pebbles are delivered from the lower portion 24 of the perforate side Walls, after the fines have escaped through the smaller perforations of the upper portion 25 of the side Walls.

The fines from sieve 22 may in a second and similar revolving sieve 26 be separated into sand of different grades or degrees of fineness.

Referring again to Figs. III and IV, my invention will be seen to involve a division of the mass of material under treatment into a plurality of parts, in this instance two parts A and B, severally scrubbed in the two scrubbers constituted by the concentric shell parts 12 and 72; and it Will be seen that, in consequence of such division, the scrubbing action is more effective. The provision of Wings Within the blind shell portions 12 and 72 greatly increases the scrubbing effect.

I have described a particular piece of apparatus as a typical one suitable for the performance of the method of my invention.

I claim as my invention:

In the Washing of gravel from native deposits which contain With the desired gravel larger and undesired pebbles, and undesired adhesive masses of earthy material as Well, which consists in sifting the material into coarser and finer subdivisions, scrubbing both divisions, and by scrubbing dissipating the adhesive masses, carrying aWay from the scrubbed coarser division the undesired pebbles, and recombining the other parts of the treated material.

In testimony whereof I have hereunto set no hand.

y FRANCIS R. DRAVO. 

